package com.lianxi;

import java.util.HashMap;
import java.util.Map;

public class MapTest {
    public static void main(String[] args) {
        Map map = new HashMap();
        map.put("a", "aaa");
        map.put("b", "bbb");
        map.put("b", "bbb");
        map.put(null, null);
        System.out.println(map.get("b"));

        System.out.println(map.size());

        System.out.println(map.values());

        System.out.println(map.keySet());
    }
}
